The present invention relates to an internal combustion engine cooling system and a valve therefor, and, more particularly, relates to an internal combustion engine cooling system and a valve therefor which provide either combined cooling for a cylinder head and a cylinder block of the engine, or either partly or totally separated cooling for the cylinder head and the cylinder block, according to operational conditions.
The concept of the present invention is based upon a prior art engine cooling system and method developed by a colleague of the present inventor, for which previous concept Japanese Patent Application No. 68036/80 was filed previously to the filing on Dec. 2, 1980 of the parent Japanese patent application No. 169933/80 of the present application of which priority is being claimed in the present application, and for which prior art concept also it is known to the present inventor that U.S. patent application Ser. No. 264,866 has been filed with the filing date of May 18, 1981 previously to the filing of the present application claiming the priority of said previous Japanese application, said previously applied Japanese and U.S. patent applications relating to said prior art concept being invented by a different inventor than but being assigned to the same assignee as the present application; and the present inventor hereby desires to acknowledge his debt to this previous proposal, and to incorporate the subject matter of that previous U.S. patent application by reference into the present application, by way of background prior art.
There are various considerations which arise with regard to the cooling of internal combustion engines which are cooled by the circulation of cooling fluid in passages or cooling jackets formed in the cylinder head and in the cylinder block thereof. Some of these considerations relate to the cooling of the cylinder head, and others to the cooling of the cylinder block. Nowadays the prior art type old or conventional ways of cooling an internal combustion engine, in which the cooling fluid for the cylinder head was always completely mixed with that for the cylinder block, thus ensuring that the cylinder head and the cylinder block were always at substantially the same temperature, have become inadequate.
One of these considerations is that it is important to maximize the thermal efficiency of an internal combustion engine, and in order to do this it is effective to increase the compression ratio of the engine. However, increase of the compression ratio of the engine is limited by the occurrence of so called knocking or pinking, i.e. of detonation caused by compression ignition, not caused by any spark from a spark plug, of the air-fuel mixture within the combustion chambers of the engine. The occurrence of knocking is generally reduced by keeping the cylinder head as cool as possible, and accordingly when an internal combustion engine is being operated, especially in operational conditions in which the occurrence of knocking is a high possibility, such as high rotational speed high engine load operational conditions, it is very important to cool the cylinder head down to as low a temperature as possible, consistent with other operational considerations.
On the other hand, it is not very advantageous to cool down the cylinder block of the engine to a very low temperature, because in that case the temperature of the lubricating oil contained within the cylinder block, which is of course strongly influenced by the temperature of the cylinder block, becomes rather low, thus increasing the viscosity of this lubricating oil and causing unacceptably high mechanical energy losses in the engine. Further, because the viscosity of the lubricating oil within the cylinder block when this oil is cold, i.e. when it is not at proper operating temperature, is higher than when said lubricating oil is at operating temperature, therefore of course while this lubricating oil is cold this causes substantially increased use of fuel by the internal combustion engine, which is very wasteful. Further, if the temperature of the walls of the cylinders of the engine, i.e. the temperature of the bores thereof, becomes low, then the amount of noxious components in the exhaust gases emitted by the engine rises, which can cause a serious problem in view of the standards for control of pollution by automobiles, which are becoming more and more severe nowadays.
Another problem that occurs if the temperature of the cylinder block gets low is that wear on the various moving parts of the internal combustion engine, especially bore wear, rises dramatically. In fact, a large proportion of the wear on the bores of an internal combustion engine occurs when the engine is in the non fully warmed up condition, both because the lubricating qualities of the lubricating oil in the engine are not good at low temperatures, and also because the state of mechanical fit to which the parts of the engine are "worn in" or "run in" is appropriate to their physical dimensions when at proper engine operating temperature, and accordingly in the cold or the semi cold condition these parts do not mate together very well.
These problems that arise when the cylinder block of an internal combustion engine becomes too cold during actual running operation of the engine of course also apply with equal force during the warming up process of the internal combustion engine, after it has been started up from the cold condition and before it has attained normal operating temperature. Especially, the problem of excessive wear on the moving parts of the internal combustion engine, and the problem of excessive emission of noxious components in the exhaust gases of the internal combustion engine, are particularly serious during warming up operation. In fact, in view of this matter, it has in the past been an important design goal for internal combustion engines for the moving parts thereof to be warmed up as soon as practicable, or at any rate to be brought to an intermediate temperature higher than a very cold non operating temperature as soon as practicable.
According to these considerations, it is important to warm up the cylinder block of an internal combustion engine as quickly as possible, when the engine is started from the cold condition, and to keep the cylinder block at quite a high operating temperature thereafter. A difficulty arises in this regard, because during the operation of an internal combustion engine most of the heat which is being generated in the combustion chambers thereof by combustion of air-fuel mixture therein is in fact communicated not to the cylinder block of the engine, but to the cylinder head thereof. Therefore transfer of heat from the cylinder head wherein said heat is generated to the cylinder block is very important, especially during the warming up process of the engine. Of course, such heat transfer can take place by the process of heat conduction, since the cylinder head is clamped to the cylinder block, typically however with the interposition between of a head gasket which may have a rather low heat conductivity. However, it is desirable to convey heat from the cylinder head to the cylinder block, during engine warmup, more quickly than can be accomplished by this conduction process, and the conventional above described mixing of the cooling fluid circulating within the cylinder head with the cooling fluid circulating within the cylinder block, during engine warmup, is effective for achieving this.
Therefore in the above mentioned prior patent application, it was proposed to provide, for an internal combustion engine comprising: (a) a cylinder head formed with a head cooling jacket for cooling said cylinder head, said head cooling jacket being formed with a cylinder head inlet and a cylinder head outlet; (b) a cylinder block formed with a block cooling jacket for cooling said cylinder block, said block cooling jacket being formed with a cylinder block inlet and a cylinder block outlet; and (c) a radiator formed with an inlet and an outlet: a cooling system, comprising: (d) a first pump for impelling cooling fluid through said head cooling jacket from said cylinder head inlet towards said cylinder head outlet; (e) a second pump for impelling cooling fluid through said block cooling jacket from said cylinder block inlet towards said cylinder block outlet; (f) a block output fluid temperature sensor for sensing the temperature of the cooling fluid which passes out through said cylinder block outlet of said block cooling jacket, and for generating a sensed block output temperature signal representative of said temperature; (g) a block recirculation conduit system leading from said cylinder block outlet of said block cooling jacket so as to supply flow of cooling fluid, from a downstream part of said block recirculation conduit system, to said cylinder block inlet of said block cooling jacket; (h) a main recirculation conduit system, an upstream part of which is communicated to said cylinder head outlet of said head cooling jacket, and a downstream part of which is communicated to said inlet of said radiator; (i) a radiator output conduit system, leading from said outlet of said radiator both to said cylinder head inlet of said head cooling jacket and also to said cylinder block inlet of said block cooling jacket, said downstream part of said block recirculation conduit system being thereby communicated also to said cylinder head inlet of said head cooling jacket; (j) a first control valve for controlling flow of cooling fluid through said radiator according to a radiator flow regulation signal; (k) a flow mixing conduit which communicates a part of said main recirculation conduit system with a part of said block recirculation conduit system; (l) a second control valve for controlling flow of cooling fluid through said flow mixing conduit according to a block flow regulation signal; and (m) a controller, which receives said sensed block output temperature signal from said block output fluid temperature sensor, and which produces, based thereon, said radiator flow regulation signal which is sent to said first control valve, and also said block flow regulation signal which is sent to said second control valve.
According to such a prior art structure, the controller can vary the amount of cooling operation provided for the internal combustion engine, by varying the opening amount of the first control valve, thus varying the amount of cooling fluid passing through the radiator, and can also vary the amount of mixing between the cooling circuit for the cylinder head and the cooling circuit for the cylinder block, by varying the opening amount of the second control valve, thus varying the amount of cooling fluid passing through the flow mixing conduit.
Further, according to a particular aspect of the above mentioned prior art, a method for operating the cooling system described above when said cooling system is filled with cooling fluid was proposed, comprising the processes, simultaneously performed, of: (o) operating said first pump and said second pump; and (p) depending upon said sensed block output temperature signal from said block output fluid temperature sensor, performing either one or the other but not both of the following two processes (q) and (r): (q) if said sensed block output temperature signal from said block output fluid temperature sensor indicates a cooling fluid temperature at said cylinder block outlet of said block cooling jacket of less than a certain first predetermined temperature value, then simultaneously: (q1) controlling said first control valve, by said radiator flow regulation signal from said controller, so as substantially to interrupt flow of cooling fluid through said radiator; and (q2) controlling said second control valve, by said block flow regulation signal, so as to allow a flow of cooling fluid through said flow mixing conduit; (r) if said sensed block output temperature signal from said block output fluid temperature sensor indicates a cooling fluid temperature at said cylinder block outlet of said block cooling jacket of greater than said first predetermined temperature value, then simultaneously: (r1) controlling said first control valve, by said radiator flow regulation signal from said controller, so as to allow cooling fluid to flow through said radiator; and (r2) controlling said second control valve, by said block flow regulation signal, so as to allow a controlled flow of cooling fluid through said flow mixing conduit.
According to such a method, during the warming up process of the internal combustion engine, before the cooling fluid which passes out through the cylinder block outlet of the block cooling jacket has attained the first predetermined temperature, the cooling systems for the cylinder head and for the cylinder block are substantially communicated, and no substantial cooling is provided for either by the radiator, so that the heat which is supplied to the cooling fluid within the head cooling jacket is communicated to the cooling fluid within the block cooling jacket, and both the cylinder head and the cylinder block are quickly warmed up together; but, after the cooling fluid which passes out through the cylinder block outlet of the block cooling jacket has attained the first predetermined temperature, then according to process (r1) substantial cooling is provided for the cooling fluid in the head cooling jacket, while according to process (r2) the amount of cooling provided for the cooling fluid in the block cooling jacket is regulated. Thus, after the internal combustion engine has been warmed up, the cylinder block may be kept substantially warmer than the cylinder head.
Further, according to a particular aspect of the the above mentioned prior art, a method of the sort described above was proposed, said cooling system further comprising an engine lubricating oil temperature sensor for detecting the temperature of lubricating oil contained within said cylinder block, and for producing a lubricating oil temperature signal representative thereof, said lubricating oil temperature signal being supplied to said controller, wherein in process (r) the opening amount of said second valve is so controlled, by said block flow regulation signal, as to allow such an amount of cooling fluid to flow through said flow mixing conduit as to keep the sensed block output temperature signal produced by said block output fluid temperature sensor approximately at a level indicative of a second predetermined temperature, except that if the engine lubricating oil temperature signal produced by said engine lubricating oil temperature sensor is indicative of a lubricating oil temperature of the lubricating oil contained within said cylinder block of higher than a third predetermined temperature, then such a block flow regulation signal is supplied to said second control valve as to cause said second control valve to open to the maximum amount; wherein said second predetermined temperature is substantially higher than said first predetermined temperature; wherein said third predetermined temperature is substantially higher than said second predetermined temperature; and wherein in process (r), if said temperature indicated by said sensed block output temperature signal is substantially higher than said second predetermined temperature, and is less than said third predetermined temperature, then said second valve is so controlled, by said block flow regulation signal, as to open up said second valve wider so as to decrease its flow resistance; and, if said indicated temperature is substantially lower than said second predetermined temperature, said second valve is so controlled as to make said second valve more closed so as to increase its flow resistance.
According to such a method, by a feedback control, the cooling fluid temperature at said cylinder block oulet of said block cooling jacket is controlled to be substantially equal to said second predetermined temperature, except in said emergency case when the temperature of said lubricating oil contained within said cylinder block rises to higher than said third predetermined temperature which is the danger temperature.
The above described prior art proposal was quite good, within its sphere; but the requirement for such a controller, operating according to such a type of logic, inevitably meant in practice that an electric or electronic controller needed to be provided, and thus the above mentioned control valves were required to be electrically operated valves, and the temperature sensors were also required to be electrical output sensors.